This item has maybe discussed before, but I did not find any results in searching the forums.
After seeing this pic of the Martinair retrojet (B767 PH-MCL) I noticed a small window (hole) just left of the front maindeck door on the right side of the aircraft. (half in the read cheat-line).
A search in the database showed me that more boeing 767's they have a similar window/hole too.

It is indeed the emergency escape slide illumination light. It is activated at the same time as the cabin interior emergency lights, ie,. when a/c power is lost. You'll also find a similar light for the overwing escape slide (if the aircraft is fitted with overwing exits, not all 767's have them)

Emergency Evacuation area illumination lights.They normally cover the Area of the escape slide to provide Battery electrical supply,as in an emergency at night,one would need lighting to exit on the slides & evacuate.
regds
MEL